The lower parts of warm, thick continental crust can flow in a ductile fashion to accommodate thinning of the upper brittle crust during extension. Naturally occurring continental rifts with a rift-axis parallel deformation gradient imply an underlying rotational component. In such settings, rift-parallel crustal flow transports material perpendicular to the direction of rifting. We use analog experiments to investigate rotational rifting and coeval crustal flow. To test the effect of rift-axis parallel flow on rift evolution, we use different gravitational loads resulting in a range of horizontal pressure gradient magnitudes which drive horizontal lower-crustal flow. The use of (three dimensional) 3D Digital Volume Correlation techniques on X-ray CT data combined with 3D Digital Image Correlation techniques applied to topographic stereo images provides detailed insights on the contemporaneous evolution of ductile flow patterns and brittle rift structures, respectively. Our results depict a complex flow field in the ductile lower crust during rotational rifting with: (a) extension-parallel horizontal inward flow and vertical upward flow that compensates thinning of the brittle upper crustal layer; (b) rift-axis parallel lateral flow, that compensates greater amounts of thinning further away from the rotation axis; and (c) different degrees of mechanical coupling between the brittle and viscous layers that change during rift propagation. Our analog experiments provide insights into ductile lower crustal flow patterns during rift evolution. The results emphasize the three dimensionality of rifting, which is an important effect that should be considered when estimating the amount of crustal extension from two dimensional (2D) cross sections.

中文翻译：

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旋转延伸促进同时代上地壳脆性断层和深部裂谷轴平行流：从模拟模型实验推断的动态耦合过程

温暖、厚实的大陆地壳的下部可以以延展的方式流动，以适应上层脆性地壳在伸展过程中变薄。具有裂谷轴平行变形梯度的自然发生的大陆裂谷意味着潜在的旋转分量。在这样的环境中，平行裂谷的地壳流动以垂直于裂谷的方向输送物质。我们使用模拟实验来研究旋转裂谷和同期地壳流动。为了测试裂谷轴平行流对裂谷演化的影响，我们使用不同的重力载荷，产生一系列水平压力梯度大小，驱动水平下地壳流动。在 X 射线 CT 数据上使用（三维）3D 数字体积相关技术与应用于地形立体图像的 3D 数字图像相关技术相结合，分别提供了关于韧性流动模式和脆性裂谷结构的同时演变的详细见解。我们的结果描述了旋转裂谷过程中韧性下地壳中的复杂流场：（a）伸展平行水平向内流动和垂直向上流动，补偿了脆性上地壳层的变薄；(b) 裂谷轴平行横向流动，补偿远离旋转轴的更大量的变薄；(c) 在裂谷扩展过程中发生变化的脆性层和粘性层之间不同程度的机械耦合。我们的模拟实验提供了对裂谷演化过程中韧性下地壳流动模式的见解。结果强调了裂谷的三维度，这是从二维（2D）横截面估计地壳伸展量时应考虑的重要影响。